Gold and Bronze: Seasonic Power Supply Units Roundup. Page 2

We are going to talk about four power supply units from Seasonic, three of which continue the legendary S12 series, while the fourth is a completely new product, the first flagship model in the X family.

The 520-watt model has a similar selection of connectors (it has a 4+4-pin CPU connector instead of a 4-pin one, but it will only be necessary for server mainboards which need two CPU power cables to be plugged in):

Mainboard cable with a 20+4-pin connector (54 cm)

CPU cable with a 4+4-pin connector (53 cm)

CPU cable with an 8-pin connector (55 cm)

Graphics card cable with a 6-pin connector (55 cm)

Graphics card cable with a 6+2-pin connector (58 cm)

One cable with three PATA power connectors (38+10+10 cm)

One cable with three PATA power connectors (50+10+10 cm)

One cable with three SATA power connectors (40+10+10 cm)

One cable with three SATA power connectors (48+10+10 cm)

The two models differ in terms of wire sections. The lower-wattage model has rather thin PATA and SATA cables (20AWG) while the cables of the higher-wattage model are all the same thickness (18 AWG).

Included with both PSUs are adapters from PATA power connectors to floppy-drive connectors (about 10 cm long).

These connectors are sufficient for building a modern gaming machine with one top-end graphics card but I can note again that the second CPU cable is only necessary for owners of server mainboards. I also think that the first CPU cable shouldn’t be shorter than 60 centimeters. Otherwise it may turn to be too short in popular system cases with a bottom PSU compartment and a space behind the mainboard reserved for hiding the cables. You can use extension cables then, but they are not very reliable, especially for computer configurations with top-end CPUs.

Compatibility with UPSes

Oddly enough, these very similar PSUs behave differently in this test: the S12-II 420 worked with my APC SmartUPS SC 620 at loads up to 350 watts but I could not make the S12-II 520 stable as it would shut down even at a load of 300 watts when the UPS switched to its batteries.

I didn’t examine the circuit design of these PSUs closely, so I cannot tell you the reason for this discrepancy. It may be due to a difference in some component ratings or in the implementation of the active PFC devices in these two models.

Output Voltage Stability

Both PSUs are very good for models with joint voltage regulation. Their voltages deflect no more than 3% in the typical load range of modern computers. It is only when the load is greatly misbalanced towards the +5V and +3.3V rails that the output voltages deflect more than the acceptable 5%. On the other hand, the S12-II series are of course inferior to PSUs with dedicated voltage regulation.

Output Voltage Ripple

The output voltage ripple is rather low at full load. The PSUs meet the industry requirements in this respect.

Noise

Each model is cooled by a 120x120x25mm fan from ADDA that has a max speed of 2050 RPM.

Both PSUs are very quiet at loads up to 200 watts, especially the 520W model. Alas, the fans accelerate quickly at higher loads, making both PSUs noisy at 300 watts. The fans produce a powerful din at the maximum speed.

Efficiency and Power Factor

Being over 85% efficient through most of the load range, these PSUs deservedly sport the 80+Plus Bronze certification.

Standby Source

The standby source copes with the full load of 2.5 amperes easily in each PSU.

Summary

The Seasonic S12-II Bronze series includes mainstream products. Moreover, the S12-II has lost the dedicated voltage regulation which used to be implemented in the Seasonic S12 we tested about four years ago. It has also become louder at medium and high loads. So, if you’ve got an S12, you shouldn’t try to upgrade it with the newer version because you won’t get any benefits other than higher efficiency. The downside of the newer PSUs is that the top-wattage model was unstable with the UPS.

Anyway, I would recommend this series for mainstream computers, including gaming configurations with one single-processor graphics card, as high-quality and quiet power supplies.